Generator regulator



Jan. 1, 1946. J. E. DIEHL 2,392,127

GENERATOR REGULATOR Filed April 29, 1943 INVENTOR. :ZKTNiU-En I db 4 M M 9 i av, arroe/vsrs.

Patented Jan. I, 1946 2' UNITED STATES PATENT OFFICE 7' GENERATOR REGULATOR John E. Diehl, St. Marys, Pa., assignor to Stack pole Carbon Company, St. Marys, Pa., 2. corporation of Pennsylvania Application April 29, 1943, Serial No. 484,959

10 Claims.

This invention relates to apparatus for automatically regulating the output of generators, by which is meant either their voltage output or their current output, or both. The invention is more particularly directed toward a generator regulator of the step type.

One of the big problems in aviation type voltage regulators is maintenance of the contacts which are used to shunt the resistors in and out of the field circuit. At present, there are two types of regulators using this method of opera-' tion which are giving considerable trouble. In one of these a series of contact leaves is touched by a bar in such a manner that as the bar moves, more and more of the leaves are engaged by the bar. The motion of the bar is controlled by a magnetic coil energized by the voltage of the generator. The other type of regulator uses a group of small leaf springs having contacts on both sides of each leaf. The leaves are placed in a stack with their contacts'normally spaced a short distance apart and with the leaves connected by electrical resistance. As pressure is applied to the stack by means controlled by the generator voltage, the contacts close one after another until enough resistance is shorted out of the circuit to hold the voltage at the desired value.

In both types of regulators just mentioned the problem is to maintain low resistance contacts without welding or sticking throughout the entire life of the regulator. This has been found impossible under all conditions since there is a tendency for contact materials to transfer under the slight arcing effect which takes place, thus leading to sticking and welding and lack of regulation. Moreover, small amounts of dust and dirt may accumulate on the contact faces and insulate them, thereby preventing the regulator from operating.

In another type of generator regulator a, rheostat is operated by a small electric motor. The motor is controlled by a reversing switch sensitive to the voltage of the generator. A'difiiculty with such a regulator is that the time lag required to compensate for an sudden change in the operating conditions at the generator isso long that the regulator cannot be used with gencraters operated: in parallel. Hunting or 0vershooting-becomes a major problem also.

It is among the objects of this invention to provide a generator output regulator of the step type which has contacts that do not weld, stick, or become insulated; which is sensitive and accurate; which does not hunt; and. which may be used quite simply to operate from either the voltage or the current of the generator, or both if desired.

In accordance with this invention an electric contact member slidably engages an electrical resistor and both are connected in series in the field circuit of an electric generator whose voltage or current is to be regulated. Connected to the armature circuit of the generator is an electromagnet that is controlled by an electric switch in series with it. Means, such as a solenoid, is connected across the generator armature or in series with it, depending upon whether the volt age or the current of the generator is to be regulated, and is thus energized sufficiently by the generator output when it reaches a predetermined value to actuate the switch. Mounted adjacent the magnet is a vibratable armature which is normally spaced from the magnet but which is adapted to be drawn toward it every time the magnet is energized upon closing of the switch. This armature is operatively connected to the sliding contact member, such as by a common shaft, in order to slide the latter on the resistor in accordance with the movements of the armature toward and away from the magnet. As the switch contacts vibrate so rapidly that the armature can move only a short distance back and forth, the resistor contact member likewise is vibrated or slid back and forth in a short path and the generator output thereby is, kept substantially constant. In case generator speed or load conditions are changed, the armature changes its position relative to the magnet and thereby quickly moves the resistor contact member to a new position where it vibrates in the same way as before. Hunting is avoided by connecting the contact member to a dashpot that keeps it from overshooting its proper position on the resistor;

The invention is illustrated in the accompanying drawing in which the figure is a more or less diagrammatic perspective view of my generator regulating apparatus.

Referring to the figure, a shunt wound gen.- erator I has current leads 2 and 3 extending away from it with one-of them connected directly toits field coil 4. The other end of the field coil is-eonnected to the other lead indirectly through the regulator that forms this invention. More specifically, the field coil is connected by a wire t to one of a pair of resistance elements 1 of the step type. The other resistance element is connected by a wire 8 to lead 3 of the generator. Each resistance element preferably resembles a portion of a commutator formed from a series of adjacent contact segments l that are insulated from one another by insulating spacers H, The contact segments are connected by short wires I 2 to a common resistance wire l3 that inserts electrical resistance between each adjacent pair of segments. The two resistance elements are electrically connected by a contact arm l5 provided at its opposite ends with electric brushes l6 that slidably engage the smooth sides of the contact segments. This arm is rigidly mounted at its center on a shaft I! that is oscillatably mounted at its ends in supporting bearing members [8. The arm is normally held in the position shown, in which it bridges the end segments to which field circuit wires 6 and 8 are attached, by a coil spring 20 that is fastened to the lower end of the arm and to a suitable fixed supporting member 2|. In this position the resistance elements I do not place any resistance in the field coil circuit; If, however, the contact arm is swung in a clockwise direction as viewed in the drawing, it will engage contact segments that are connected to the end segments only through the resistance wires l3 and will thereby add electrical resistance to the field coil circuit. The resistance inserted between the segments is of such a value that the voltage drop between each adjacent pair of segments will be the same when the current is being switched through and around these segments. This reduces to a minimum any tendency for an arc to be drawn between the contact arm and the segments; equally distributing over the entire set of segments any such tendency rather than permitting it all to be present between any one pair.

For turning shaft I! so as to move the contact arm across the resistance elements, an armature bar 24 is rigidly mounted at its center on the opposite'end of the shaft. The lower half of this bar projects between the opposite ends of an electromagnet core of peculiar shape. Thus, as shown, the core has a vertical leg 25 on which the coil 26 of the magnet is wound, and a bottom horizontal leg 21 that has an upwardly extending end with an inclined face 28. The top of the vertical leg has a laterally projecting portion with an end face 29 having the same radius as face 28. These two faces have the same center of curvature. The bar 24 has end faces 30 shaped to give a uniform increase in torque as they are drawn from the position shown toward the ends of the magnet core. When the magnet is energized, the magnetic field that is created attracts the armature and swings it in a clockwise direction towards the ends of the core. This turns shaft I! which moves contact arm 15 across the resistance elements and thereby adds resistance to the field coil circuit. When the magnet is deenergized, coil spring 20 swings the contact arm and armatur in the opposite direction back toward their original positions.

In order to control the electromagnet, one end of its coil 26 is connected to one of a pair of normally spaced or open switch contacts, preferably a fixed contact 3|. The other contact 32 is mounted on one end of a metal arm 33 that is pivoted on its transverse axis on any suitable support 34. The contact end of the arm normall is held in raised position by an adjustable calibrated coil spring 36 attached to its opposite end and to a suitable support 31 below it. The arm is electrically connected to generator lead 3 by a flexible Wire 38.

For the purpose of moving the upper contact down'against the fixed contact 3| so to close the switch to energize the electromagnet, an armature button 40 is secured to the bottom of arm 33 between the movable contact and support 34. This armature is directly above and normally spaced from the upper end of the core 4| of a solenoid. The upper end of the solenoid coil 42 is connected to the switch arm, and the lower end of the coil is connected through a variable resistance 43 to the generator lead 2.

When the generator voltage reaches a predetermined value for which the switch has been set, it energizes solenoid coil 42 sufficiently to cause it to draw armature button 40 toward it. This pulls the switch arm down against the resistanc of spring 36 until contact 32 strikes fixed contact 3| and thus closes the switch. The electromagnet is thereby connected in the generator armature circuit and is electrically energized by the generator voltage. The magnetic field set up by the magnet causes armature bar 24 to swing toward the opposite ends of the magnet. Turning of shaft 11 moves contact arm l5 along the resistance elements 1 so that resistance 13 is added to the field coil circuit. The added resistance decreases the generator voltage, so switch spring 36 overcomes the magnetic attraction of the solenoid and opens the switch contacts. This opens the magnet circuit, whereupon the spring 20 attached to contact arm l5 starts to swing the arm and armature bar back to their original positions illustrated. Before the arm has moved across more than one or two contact segments, sufiicient resistance is taken out of the field coil circuit to permit the generator voltage to rise againto the pointwhere it causes the switch solenoid to close the switch. With the magnet once more in circuit,-it again attracts its armature bar, thereby adding resistance to the field coil circuit and causing the switch to open. It will be seen that the switch contacts vibrate so rapidly that contact arm I5 does not have a chance to move more than a short distance in either direction on the resistance elements. As a result, with the generator operating under any given speed and load conditions, the amplitude of vibration of the armature bar and the contact arm is just great enough to hold the generator voltage substantially constant.

In case the speed of the generator is changed or the load on it is varied, there naturally will tend to be a more pronounced change in the voltage output. If it is an increase, the armature bar will be swung closer to the ends of the magnet than before and the contact arm will therefore add more resistance to the field coil circuit to keep down the voltage. If the voltage is decreased, less resistance will be added. In either case, to prevent a sudden change from movin the contact arm too far along the resistance elements and beyond the new position it should take, which would cause hunting, a dashpot or the like is connected to the arm to keep it from overshooting. Thus, the upper end of the arm may be pivotally connected by a rod 45 to a piston 46 reciprocable in a cylinder 41. One end of the cylinder is open, but the other end is closed except for a small adjustable port 48 through which air canslowly enter and leave the chamber formed between the closed end of the cylinder and the adjacent end of the piston. This restrains the contact arm from changing its regulating position so fast as to overshoot the contact segments that it should engage forregulation under a new set of conditions.

The sliding motion of brushes I6 against contact segments 1 I prevents any build-up or transfer-of contact material and thus eliminates the problems of sticking and welding. The motion ofv the brushes also tends to keep the contact surfaces free of any material which would insulate them. Thus, two of the main problems involved in step-type regulators are eliminated by this invention. This regulator is sensitive to voltage changes the same as Tirrill type regulators, and its speed reaction is comparable to them and is much more rapid than that of a motor operated rheostat type regulator.

In order to still further decrease the tendency of the generator to hunt, it is desirable to wind a coil 50 on solenoid core 4| and to connect one end of this coil to electromagnet coil 26 and the other end to a variable resistance 5| connected to generator lead 2. This coil thus is operated by the voltage across the electromagnet.

To help parallel generators to distribute their loads, another .coil 54 may be wound on the solenoid core and connected across a resistor 55 in lead 2. The generator side of the resistor is connected to an equalizing line 56 that connects in like manner to other generators and their regulators in parallel with the one shown. Coil 54 is thus energized by the voltage drop across the resistor in such a manner as to cause the generator voltage to decrease with an increase in load. current and vice versa. The coil is energized to a greater or lesser degree depending upon the amount of current being drawn from the generator. This prevents one generator from producing more than its share of the load in parallel operation; that is, by dropping its voltage when it would tend to produce more than its share of power.

' This regulator may be used for regulating the current output of a generator rather than its voltage output by merely connecting solenoid coil 42 in series in output lead 2 or 3 or across a resistor in one of those leads instead of across the generator armature. Or, by using such a relay with the one illustrated and with their contacts connected in parallel so that either or both of the relays may energize coil 26, both the current and the voltage of the generator may be controlled.

According to the provisions of the patent statutes, I have explained the principle and construction of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A regulating rheostat comprising an electrical resistor, an electric contact member slidably engaging the resistor, an electromagnet, an electric switch connected in series with the magnet, said magnet and switch being adapted to be connected in an electric circuit, electrically responsive means for periodically actuating the switch whereby the magnet is alternately energized and deenergized, a vibratable armature for the magnet normally spaced therefrom but adapted to be drawn toward it when the magnet is energized, and means operatively connecting said armature to said contact member to slide the latter on said resistor in one direction when the armature is drawn toward the magnet and in the opposite direction when the armature moves away from the magnet.

2. A regulating rheostat comprising an electrical resistor, an electric contact member slidably engaging the resistor, an electromagnet, an electric switch connected in series with the magnet, said magnet and switch being adapted to be con nected in an electric circuit, a solenoid for periodically actuating the switch whereby the magnet is alternately energized and deenergized, a vibratable armature for the magnet normally spaced therefrom but adapted to be drawn toward it when the magnet is energized, and means rigidly connecting said armature to said contact member to slide the latter on said resistor in accordance with the movements of the armature.

3. A regulating rheostat comprising an electrical resistor, an electric contact member slidably engaging the resistor, an electromagnet, an electric switch connected in series with the magnet, said magnet and switch being adapted to be connected in an electric circuit, a solenoid for periodically actuating the switch whereby the magnet is alternately energized and deenergized, a vibratable armature for the magnet normally spaced therefrom but adapted to be drawn toward it when the magnet is energized, means operatively connecting said armature to said contact member to slide the latter on said resistor in accordance with the movements of the armature, and a winding on said solenoid connected across the magnet to decrease any tendency of said contact member to hunt.

4. A regulating rheostat comprising an electrical resistor, an electric contact member slidably engaging the resistor, an electromagnet, an electric switch connected in series with the mag net, said magnet and switch being adapted to be connected in an electric circuit, electrically responsive means for periodically actuating the switch whereby the magnet is alternately energized and deenergized, a vibratable armature for the magnet normally spaced therefrom but adapted to be drawn toward it when the magnet is energized, and an oscillatably mounted shaft rigidly connecting said armature to said contact member to slide the latter on said resistor in accordance with the movements of the armature.

5. A regulating rheostat comprising an electrical resistor, a shaft mounted for oscillation on its axis, an electric contact arm mounted on the shaft and projecting radially therefrom into sliding engagement with the resistor, an electromagnet, an electric switch connected in series with the magnet, said magnet and switch being adapted to be connected in an electric circuit, electrically actuated means for periodically actuating the switch whereby the magnet is alternately energized and deenergized, and a vibratable armature mounted on said shaft and projecting radially therefrom adjacent the magnet, said armature normally being spaced from the magnet but being adapted to be swung toward it when the magnet is energized whereby to slide said contact arm on said resistor.

6. A regulating rheostat comprising an electrical resistor, an electric contact member slidably engaging the resistor, an electromagnet, an electric switch connected in series with the magnet, saidmagnet and switch being adapted to be connected in an electric circuit, electrically actuated means for periodically actuating the switch whereby the magnet is alternately energized and deenergized, a vibratable armature for the magnet normally spaced therefrom but adapted to be drawn toward it when the magnet is energized, means operatlvely connecting said armature to said contact member to slide the latter on said resistor in accordance with the movements of the armature, and a dashpot operatively connected to the contact member to restrain excessive movement thereof.

7. A regulating rheostat comprising apair of spaced electrical resistors, a shaft mounted for oscillation on its axis between the resistors, an electric contact arm mounted on the shaft and projecting radially therefrom in opposite directions into sliding engagement with said resistors, said arm electrically bridging said resistors, an electromagnet, an electric switch connected in series with the magnet, said magnet and switch being adapted to be connected in an electric circuit, electrically responsive means for periodically actuating the switch whereby the magnet is alternately energized and deenergized, and a vibratable armature mounted on said shaft and projecting radially therefrom adjacent the magnet, said armature normally being spaced from the magnet but being adapted to be drawn toward it when the magnet is energized whereby to slide said contact arm on said resistor.

8. A regulating rheostat comprising an electrical resistor, a shaft mounted for oscillation on its axis, an electric contact arm rigidly mounted on the shaft and projecting radially therefrom into sliding engagement with the resistor, an electromagnet having a generally U-shape core, an electric switch connected in series with the magnet, said magnet and switch being adapted to be connected in an electric circuit, electrically responsive means for periodically actuating the switch whereby the magnet is alternately energized and deenergized, and a vibratable armature rigidly mounted on said shaft and projecting radially therefrom in opposite directions adjacent the magnet, the ends of said armature normally being spaced from the ends of the magnet core but being adapted to be swun toward them when the magnet is energized whereby to slide said contact arm on said resistor.

9; A regulating rheostat comprising an electrical resistor, an electric contact member slidably engaging the resistor, an electromagnet, an electric switch connected in series with the magnet, said magnet and switch being adapted to be connected in an electric circuit, a solenoid for periodically actuating the switch whereby the magnet is alternately energized and deenergized, a vibratable armature for the magnet normally spaced therefrom but adapted to be drawn toward it when the magnet is energized, means operatively connecting said armature to said contact member to slide' the latter on said resistor in accordance with the movement of the armature, an electrical resistance adapted to be connected in an electric circuit, and a winding on said solenoid connected across said resistance.

10. A regulating rheostat comprising a commutator-like member formed from a plurality of spaced contact segments electrical resistances connecting the segments with one another, an electric contact member slidably engaging said segments, an electromagnet, an electric switch connected in series with the magnet, said magnet and switch being adapted to be connected in an electric circuit, electrically responsive means for periodically actuating the switch whereby the magnet is alternately energized and deenergized, a vibratable armature for the magnet normally spaced therefrom but adapted to be drawn toward it when the magnet is energized,

and means operatively connecting said armature to said contact member to slide the latter on said segments in accordance with the movements of the armature.

JOHN E. DIEHL. 

